"I beg your pardon, it HAS been discovered."
"By whom?"
"By me!"
"By you?"
"You may readily believe that otherwise I should not have risked this expedition across Africa in a balloon. In twenty-four hours I should have been without gas!"
"But you said nothing about that in England?"
"No! I did not want to have myself overhauled in public. I saw no use in that. I made my preparatory experiments in secret and was satisfied. I have no occasion, then, to learn any thing more from them."
"Well! doctor, would it be proper to ask what is your secret?"
"Here it is, gentlemen--the simplest thing in the world!"
The attention of his auditory was now directed to the doctor in the utmost degree as he quietly proceeded with his explanation.
CHAPTER TENTH
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Former Experiments.--The Doctor's F
